30 December 2010

A very seasonal camera

One of my (no doubt many) personal oddities is a love of revisiting the basics of photography. Obsolete methods, sometimes; calotype, cyanotype, gum bichromate and the rest. Pinhole sometimes; my crowning achievement in that direction was a zoom pinhole camera with multiple A5 dark slides. But my particular fascination is with building conventional optical cameras, preparing conventional silver halide emulsions, brewing conventional chemistries, all from scratch materials.

I don't do this all the time, you understand. Just every now and then, when the moon is full, there's an "R" in the month, and the mood takes me.

The most recent adventure started with finding an incredibly poor quality plastic magnifying "glass" in a christmas cracker. Text examined through it waves and ripples and blurs beautifully. A quick test projection onto a wall of the world outside the nearest window established that it has a focal length of 150mm, which in turn suggested[1] a 105×105mm piece of film.

In practice, though, the image circle diameter was only abut 100mm, and the largest piece of spare photographic material to hand was a long out of date 120 roll of Kodak VPS. Take those two facts together, and an image size of 60×75mm emerges[2].

All which happened to conveniently fit with the size of a discarded mince pie packet.

Thus was a seasonal camera born: mince pie body, cracker lens. A seasonal subject was obviously needed ... a candle in a frosted glass fit the bill nicely.

I didn't mix the chemistry myself; a friendly lab tapped off a cupful of each required solution from their waste line. Scanning the dried result produce the image you see here... (as usual, double click it for a larger view)

[1] The rule of thumb is that, to roughly match normal human vision at rest, image diagonal should approximate to focal length.

[2] Pythagoras' theorem

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